1. Field of the Invention
This invention relates to a thermoplastic, segmented, linear copolyesterether elastomer having soft segments derived from a poly(alkylene oxide) glycol. More particularly, the invention concerns such an elastomer having poly(1,3-propylene terephthalate) hard segments.
2. Description of the Prior Art
Various thermoplastic, linear polyetheresters elastomers have been suggested for the production of molded articles, films and fibers. Such polyetheresters are known, as for example, from Shivers, U.S. Pat. No. 3,023,192, Witsiepe, U.S. Pat. No. 3,651,014, Wolfe, U.S. Pat. No. 3,775,374, Bell et al, U.S. Pat. No. 3,243,413, Nishimura, et al, "Elastomers Based on Polyester", J. Macromol. Sci. (Chem.), A1(4), 617-625 (1967), and Wolfe, "Elastomeric Polyetherester Block Copolymers", American Chemical Society Advances in Chemistry, 176, 129-151 (1979), among others. Basically, these elastomers are composed of long chain ester units which constitute the "soft segments" of the elastomer and short chain ester units which constitute the "hard segments" of the elastomer.
I have found that thermoplastic, linear polyetherester elastomers for use in fibers or films generally require the soft segments to constitute at least 70 percent of the polyetherester elastomer. For the production of fibers or films, such elastomers having hard segments derived from poly(ethyleneterephthtalate) crystallize too slowly for satisfactory commercial manufacture; those having hard segments derived from poly(1,4-butylene terephthalate) crystallize well but provide fibers that would benefit much from improvements in elastic properties, especially, in set and unload power. Such improved elastomers would be particularly useful for conversion into fibers or films intended for elastification of diaper legs, among other articles. Accordingly, an object of this invention is to provide a thermoplastic linear polyetherester elastomer that can be converted into fibers or films having the above-mentioned desired combination of properties.